Which of the following best describes isobars?

• A. Atoms of the same element that have the same number of neutrons
• B. Atoms of different elements that have the same atomic number but different mass numbers
• C. Atoms of the same element that have different numbers of neutrons
• D. Atoms of different elements that have the same mass number but different atomic numbers

Answer: (D)

Verified step by step guidance

1. Recall the definition of isobars: Isobars are atoms of different elements that have the same mass number but different atomic numbers.
2. Understand that the atomic number (Z) represents the number of protons in the nucleus, which defines the element.
3. Recognize that the mass number (A) is the sum of protons and neutrons in the nucleus.
4. Since isobars have the same mass number, they have the same total number of protons plus neutrons, but because they are different elements, their atomic numbers (proton counts) differ.
5. Therefore, the correct description of isobars is: atoms of different elements that have the same mass number but different atomic numbers.